The invention relates to ink jet printers. More particularly, the invention relates to the thermal management of printheads in large format ink jet printers.
Many modern printing devices incorporate thermal ink jet technology. Typically, this technology utilizes a printhead (also known as a pen) having a silicon die supporting one or more vaporization chambers. During a printing operation, resistors or other ink ejection elements on the silicon die are heated to vaporize and eject ink through nozzles overlying the vaporization chambers, thereby causing dots of ink to be printed on a recording medium, e.g., paper.
The printhead typically sweeps across the width of the recording medium during a printing operation, and based upon the image to be printed, certain ink ejection elements are activated (i.e., heated) to eject ink through respective nozzles. By virtue of the heat applied to the ink ejection elements during the printing operation, the temperature of the silicon die, and thus the printhead, rises. Thus, generally speaking, the temperature of the printhead will change or fluctuate during the printing operation. More specifically, the temperature of the printhead will be lower when the printer is printing xe2x80x9clightxe2x80x9d areas or in a slow mode than when the printer is printing xe2x80x9cdensexe2x80x9d areas or in a fast mode. As the printhead temperature changes, it is typically preferable that the temperature of the silicon die remains below a peak temperature to avoid delamination in the printhead as a direct result of thermal stress.
In a large format ink jet printer, e.g., HEWLETT-PACKARD HP500, the printheads are typically configured to withstand a substantially large amount of heat, especially when printing heavy density images along a large swath. A swath is typically defined as the area on a print media to be printed upon during a single pass of the printhead, e.g., in a HP500 printer, a swath may be 40 inches in length. A swath may thus typically be defined as a number of dots (i.e., a height of the columns of dots) that a printhead may record during a pass along a print direction. Additionally, a swath may be printed during one or more passes across the same horizontal portion, depending upon the selected print mode. Large format ink jet printers typically control heat energy by balancing the heat energy applied to the printhead as a function of the temperature of a silicon die. However, in some print modes, e.g., a fast mode, a normal mode, and the like, the heat energy control may be insufficient to prevent the printhead from exceeding a peak temperature.
One known solution to prevent undue thermal stress in large format ink jet printers is to change the printmode behavior in response to a forecast of an incoming density per swath. In this respect, the incoming density per swath is compared to a past temperature/density to determine a new maximum print density for the incoming swath. If the predicted incoming density per swath is greater than the newly calculated maximum print density, the incoming swath height is reduced. That is, a number of nozzles located near the top and/or bottom ends of the printhead are not employed during the printing operation, thereby reducing the total number of nozzles employed and thus reducing the heat generated in the printhead.
Although the technique of reducing swath height has been found to be a substantially adequate solution, the technique suffers from several drawbacks and disadvantages. For instance, the technique may impact the print quality of the recorded image because the possibility of banding is increased. Banding is the phenomenon, which may result from an attempt to print one swath next to a second swath without providing an overlap of the swaths, such that a line or band is formed between the adjacent swaths. By virtue of the reduction of swath height, the possibility of non-overlap occurring increases, thereby increasing the potential for banding. Moreover, the above-mentioned technique may require an increased amount of time to record an image on a recording medium.
Additionally, the above-described technique implements a linear model prediction algorithm that predicts the density of a following swath. One drawback associated with most known linear models is that they may provide a prediction of an error condition of a predicted maximum density exceeding a set maximum density, but only within a few number of swaths prior to the error condition. As a result, the typical algorithm may incorrectly predict the error condition. Thus, the typical algorithm may not accurately predict when the error condition will occur. Furthermore, the above-described technique does not take into consideration sections of a swath that require a relatively large amount of ink. Thus, when evaluating the peak temperature of the printheads in printing a swath, although the actual number of ink drops may be evaluated, the above-described technique would be unable to determine whether concentrated areas of ink drops would cause the printheads to exceed a maximum temperature.
Moreover, the above-described technique may affect the throughput of the large format ink jet printer. As discussed hereinabove, because the typical algorithm may be unable to predict when the maximum density is exceeded in a sufficiently timely manner, a printer may cease or temporarily halt until the temperature of the printheads reduces to an acceptable level. As a result, a user may be required to wait a relatively unexpectedly long time for completion of the print operation.
Yet another drawback to the swath height reduction technique lies in the inaccuracy of a prediction that an error condition will be triggered. The linear models implemented by the typical prediction algorithms rely on an average of data across a total length of a swath, which in some cases may exceed forty inches. As a result, the linear model may not take into account local high-density zones in a swath. Accordingly, the swath height reduction technique may fail to accurately predict the triggering error condition.
In accordance with one aspect, the present invention pertains to a method of managing temperature in a printer. In the method, a file is preprocessed into a plurality of swaths, with each of the swaths being further preprocessed in to a plurality of cells. An estimated peak temperature is calculated for each printhead in printing each of the plurality of cells, and a swath is printed in response to the estimated peak temperature for each printhead in printing each of the cells being below a predetermined maximum temperature. Additionally, a pass of each printhead in printing the swath is divided into a number of sub-passes in response to the estimated peak temperature for each printhead in printing each of the cells being greater than the predetermined maximum temperature.
According to another aspect, the present invention pertains to a system for managing temperature in a printer. The system includes a memory, at least one printhead, and an adaptive thermal print swath servo (xe2x80x9cATPSSxe2x80x9d) module to preprocess a file stored in the memory into a plurality of swaths. Each swath is further preprocessed into a plurality of cells, such that, the ATPSS module is further configured to calculate an estimated peak temperature for each printhead in printing each cell and to print said swath with said printhead in response to said estimated peak temperature for each printhead in printing each cell being below a predetermined maximum temperature.
According to yet another aspect, the present invention pertains to a computer readable storage medium on which is embedded one or more computer programs, the one or more computer programs implementing a method for managing temperature in a printer. The one or more computer programs including set of instructions, including, preprocessing a printable file into a plurality of swaths, with each swath being further preprocessed into a plurality of cells. Calculating an estimated peak temperature of at least one printhead in printing each cell and printing the swath in response to the estimated peak temperature for each cell being below a predetermined maximum allowed temperature.
Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.